In the manufacture of fuel pellets for use in nuclear reactor fuel rods, ammonium diuranate (ADU) is precipitated from a solution of uranyl fluoride by the addition of ammonium hydroxide. The precipitated ADU is then filtered, dried, calcined, and pressed into the pellets.
The filtration of the ADU is facilitated by a rapid settling rate, so that large quantities of slurry can be quickly processed. The calcination and pellet-sintering are facilitated by a precipitate of a small particle size because the greater surface area increases the reaction rate. Unfortunately, a rapid settling rate and a small particle size are generally opposing properties because small particles do not settle rapidly.